Rotating apparatus known as trommels have long been used to screen dirt, debris, and other undesirable material from desirable material as well as to sort or size particulate material, such as grains. In general, the trommels have a cylindrical configuration defined by a skeletal framework and one or more screen panels attached thereto. The screen panels each have a plurality of sorting (or sizing) holes or apertures therein that serve to pass particulate matter therethrough below a certain size range. The particulate matter is inserted into the trommel in one end thereof and, as the trommel rotates the undersized particles are passed through the holes into the appropriate collection apparatus disposed therebelow. In this manner, grain such as seed corn, oats, barley, etc. can be sorted according to size. Many times the materials are subjected to multiple sortings, sometimes within the same overall apparatus. In addition, there are several companies that place multiple trommels within a single unit, which will be referred to as a sizer hereafter.
As the material within the trommel rotates, particles slightly too large to pass through the apertures can become lodged therein. Within a very short time of beginning the sorting or sizing operation, the screen apertures can nearly all become completely obstructed, thereby preventing anymore material from passing therethrough and essentially ending the sorting operation as it begins. To prevent this from occurring, it is known in the art to use a variety of devices to clean the screen apertures as the screen is rotated. One such device uses a plurality of cylindrical rollers mounted on a shaft for free rotation relative thereto. The shaft is disposed above the trommel in such a manner that the rollers can rollingly engage the trommel. Friction between the trommel and the rollers causes the rollers to rotate as the trommel is rotated. The rollers are typically made of wooden or other suitable material. As the trommel rotates then, the rollers engage the portions of the particulate material extending through the sorting aperture and force the material out of the apertures and back into the interior of the trommel, thus opening the apertures so they can be used to sort material as intended. Another known type of screen cleaner utilizes an elongate cylindrical brush that cleans the screens by means of the brush bristles extending into the sorting apertures as the trommel rotates, forcing the material out of the apertures.
Still another form of trommel cleaner utilizes an elongate cleaner that includes a plurality, typically few in number, of flappers that extend outward from a central hub and into contact with the trommel. The flappers extend the length of the trommel and have a rectangular cross section. These units work well in cleaning the trommel screen, but are accompanied by several deficiencies. As the elongate flapper engages the trommel along its entire length, that is, as it slaps against the trommel, knocking the stuck material from the sizing holes, a torque spike is created that must be accommodated by the drive unit. Thus, a plurality of torque spikes equal to the number of flappers is created with each revolution of the trommel cleaner. These torque spikes necessitated the use of heavier elements than would otherwise be necessary in the drive system. In addition, the torque spikes most likely shortened the lifetime of all of the elements of the trommel system. Finally, this type of trommel cleaner requires a separate drive system to drive the cleaning unit. That is, they cannot be friction driven like the rollers and must have their own drive system comprising chains (or belts) and gears (or pulleys).
It would be desirable to have a trommel cleaner that provided the cleaning advantages of the flapper cleaners but that did not create the torque spikes found in such prior art cleaners.